Reader/writer device and automatic ticket gate including the same for checking ticket

ABSTRACT

An antenna unit prevents a communication error by suppressing side lobes formed by an antenna coil segment of a reader/writer device. The antenna unit ( 200 ) is used for a reader/writer device ( 20 ) whose signal processing circuits ( 210 ) and ( 220 ) communicate with an IC card ( 10 ) via electromagnetic waves, wherein an antenna coil ( 100 ) of the IC card ( 10 ) relatively gets close to the antenna unit ( 200 ). The antenna unit ( 200 ) includes the antenna coil segment which forms a loop antenna ( 202 ) on a substrate ( 201 ) and conductor segments ( 203 ) at the periphery of the antenna coil on substantially the same plane of the antenna coil.

This application is a National Phase application of InternationalApplication No. PCT/JP03/11571, having an international filing date ofSep. 10, 2003. This application additionally claims priority to JapaneseApplication No. JP2002-267915, filed on Sep. 13, 2002.

TECHNICAL FIELD

The present invention relates to a reader/writer device and an automaticticket gate including the reader/writer device for checking tickets and,in particular, to a structure of the reader/writer device.

BACKGROUND ART

Such a wireless information transmitter/receiver includes wirelessinformation storage media (hereinafter referred to as “IC cards”) and areader/writer device. For example, the wireless informationtransmitter/receiver can be applied to an automatic ticket gate to checkpassenger tickets or an entrance control system.

The IC card has a loop antenna, an IC chip connected to terminals of theloop antenna, and a tuning capacitor on a main surface of a plastic cardsubstrate. The reader/writer device includes a loop antenna, amodulator-demodulator circuit, and a CPU. The reader/writer devicetransmits data to the IC card by flowing electric currents modulatedfrom 13.56 MHz carrier with transmitting data to the loop antenna, andreceives data from the IC card by flowing unmodulated electric currentsto the loop antenna.

When the loop antenna of the IC card gets closer to the loop antenna ofthe reader/writer device, the terminal of the loop antenna of the ICcard produces induced voltage caused by the electromagnetic induction.Accordingly, the IC chip receives stable power supply voltage anddemodulates modulated waves to receive data transmitted from thereader/writer device. When the IC chip transmits data stored in a memorythereof, the IC chip switches terminal impedance by changing the loadtherein in accordance with the data. The reader/writer device detectsthe load changes and demodulates them to receive the data from the ICcard. Thus, the IC card and the reader/writer device communicate witheach other. Subsequently, a higher level system of the reader/writerdevice, such as a computer or another external information processingsystem, utilizes the data to, for example, check passenger tickets orcontrol human entrance (refer to Japanese Unexamined Patent ApplicationPublication No. 10-13312).

In a loop antenna 202 of such a reader/writer device, a flow of electriccurrent i produces magnetic fluxes H shown in FIG. 11. The arrow withdashed line shown in FIG. 12 illustrates combined magnetic fluxes of thefluxes around the loop antenna taken along line XII—XII in FIG. 11. Thatis, inside the loop antenna 202, since directions of the magnetic fluxesgenerated along each edge of the loop antenna 202 are the same, anupward magnetic field having its maximum value at the center of the loopantenna 202 is generated. In contrast, outside the loop antenna 202, thedirection of magnetic fluxes generated along two neighboring edges ofthe loop antenna 202 is reversed from the direction of magnetic fluxesgenerated along the opposing neighboring edges. Accordingly, a downwardmagnetic field magnetic flux is generated after the magnetic fluxes arecombined.

Since a power supply of the reader/writer device is an AC power supplyof 13.56 MHz, only one side of the loop antenna 202 will be described. Amagnetic field shown by a dashed line in FIG. 13 is generated to formcommunication spaces to communicate with the IC card. That is, as shownin FIG. 13, a main communication space M, also referred to as “mainlobe”, having its maximum value at the center of the loop antenna 202,is produced inside the loop antenna 202, while smaller sub communicationspaces S, also referred to as “side lobes”, are produced at theperiphery of the loop antenna 202.

If, as shown by the arrow in FIG. 13, an IC card 10 passes from the sublobe S through the main lobe M in one direction (from left to right inFIG. 13), a communication error sometimes occurs.

That is, while the IC card 10 is passing through the first side lobe S,an induced voltage is generated in the IC card 10. The IC card 10receives initial data from the reader/writer device, and then transmitsinitial data to the reader/writer device. After the reader/writer devicereceives the initial data, the IC card 10 passes through a boundary Bbetween the side lobe S and the main lobe M, where a magnetic fieldsufficient for generating a predetermined induced voltage is notproduced. Since power supply for the IC card is temporarily blocked,only the IC card is initialized.

Subsequently, the IC card 10 enters the main lobe M. Although the ICcard attempts to receive the initial data from the reader/writer device,the reader/writer device attempts to continue the previous communicationin the side lobe S. As a result, the reader/writer device regards thiscommunication mismatch between the IC card and the reader/writer deviceas a communication error.

DISCLOSURE OF INVENTION

Accordingly, it is an object of the present invention to provide anantenna unit of a reader/writer device that prevents a communicationerror by suppressing side lobes formed in an antenna coil segment of thereader/writer device, to provide a reader/writer device and aninformation processing system including the antenna unit, and acommunication method for the antenna unit, and also to provide a methodfor manufacturing the antenna unit.

According to the present invention, an antenna unit is included in areader/writer device whose signal processing circuit communicates with awireless information storage medium via electromagnetic waves bybringing an antenna coil of the wireless information storage mediumclose to the antenna unit. The antenna unit includes a loop antenna coilsegment formed on a substrate and conductor segments formed at theperiphery of the antenna coil segment on substantially the same plane ofthe antenna coil.

According to the present invention, the conductor segments are disposedat the periphery of the antenna coil segment to suppress an occurrenceof the side lobes at the periphery of the antenna coil segment.

An electric field generated by a conductor having a uniform thickness(ideally, a perfect conductor having a uniform resistance) is formedperpendicularly on a main surface of the conductor segment. Since anelectromagnetic field formed here is perpendicular to the electricfield, no electromagnetic field perpendicular to the conductor segmentexists. Accordingly, when the antenna coil of the wireless informationstorage medium approaches the conductor segment in parallel, an inducedvoltage is not generated in the antenna coil, thus inhibiting acommunication between them. According to the present invention, sincethe conductor segments are disposed at the periphery of the antenna coilsegment, communication spaces are not created in the areas associatedwith the conductor segments. Creating such non-communication spaces inthe desired areas suppresses a communication error.

According to the present invention, the conductor segments may bedisposed at any locations in the periphery of the antenna coil segment.For suppressing the communication error, the conductor segments arepreferably disposed at all the areas in the periphery of the antennacoil segment; however, the conductor segments may be disposed at onlyareas where the communication error is likely to occur when the wirelessinformation storage medium approaches. That is, the peripheral areawhere the wireless information storage medium accidentally approachesmay depend on a mounted location of the antenna coil, the layout, andthe intended use of the reader/writer device. Selecting the appropriatelocation and area in accordance with this situation suppresses thecommunication error, miniaturizes the antenna coil segment, and reducesthe cost.

The shape of the antenna coil segment according to the present inventionmay be any shape; it may be a rectangular loop, a circular loop, or anyother shape. A rectangular loop antenna coil requires a conductorsegment at the periphery of at least one of the edges thereof.

The following modification is preferable for the present invention: Ifthe conductor segments at the periphery of the antenna coil segment areelectrically connected to each other, the conductor segments form onecoil, which may cause negative effect on the communication of theantenna coil segment. Therefore, at least part of the conductor segmentsis electrically insulated to make the conductor segments electricallydiscontinuous.

The following modification is preferable for the present invention: Theconductor segments can be formed from the same conductive pattern asthat for the antenna coil segment. To form the antenna coil segment andthe conductor segments from the same material, a conductive layer may beformed on a main surface of an insulating substrate, and then the loopantenna coil segment and the conductor segments may be formed byetching.

Creating the antenna coil segment by the conductive pattern formed onthe insulating substrate allows the conductor segments to be formed inthe same manufacturing step. A low-cost antenna unit can be providedcompared to a manufacturing method in which conductor segmentsmanufactured in another step are bonded at the periphery of the antennacoil segment. Additionally, forming the conductor segments by the sameconductive pattern as that for the antenna coil segment improves thepositioning of the conductor segments to the antenna coil segment,thereby further decreasing an occurrence of the communication errors.Furthermore, forming the conductor segments by the same conductivepattern as that for the antenna coil segment advantageously eliminatesan adjustment of the tuning frequency compared to the manufacturingmethod in which conductor segments manufactured in another step arebonded at the periphery of the antenna coil segment.

The antenna unit according to the present invention can be applied to areader/writer device in which a communication is performed between asignal processing circuit and a wireless information storage medium withelectromagnetic waves induced by coupling an antenna coil of thewireless information storage medium and the antenna coil segment.

Additionally, the antenna unit according to the present invention can beapplied to an information processing system including a reader/writerdevice in which a communication is performed with electromagnetic wavesinduced by coupling an antenna coil of a wireless information storagemedium and the antenna coil segment of the reader/writer device when thewireless information storage medium relatively gets close to thereader/writer device. The information processing system includes, forexample, a ticket gate that processes ticket data after wirelesstransmission and reception of the data, and a mobile phone and a PDAthat read information from and write information to a contactlessinformation medium.

According to the present invention, the wireless information storagemedium may be of any type. For example, it may be an IC card; however,the wireless information storage medium is not limited to a card. Forexample, the wireless information storage medium according to thepresent invention includes information technology equipment thatincorporates an IC chip therein, such as a mobile phone.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of a wireless information transmitter/receiveraccording to an embodiment of the present invention;

FIG. 2 is a diagram of the equivalent circuit of the wirelessinformation transmitter/receiver shown in FIG. 1;

FIG. 3 is a plan view of a whole antenna unit according to an embodimentof the present invention;

FIG. 4 is a sectional view taken along line IV—IV in FIG. 3;

FIG. 5 is a plan view of a whole antenna unit according to antherembodiment of the present invention;

FIG. 6 is a plan view of a whole antenna unit according to anotherembodiment of the present invention;

FIG. 7 is a plan view of a whole antenna unit according to anotherembodiment of the present invention;

FIG. 8 is a plan view of a whole antenna unit according to anotherembodiment of the present invention;

FIG. 9 is a sectional view of magnetic fluxes of the antenna unitaccording to the embodiment of the present invention;

FIG. 10 is a sectional view of a magnetic field of the antenna unitaccording to the embodiment of the present invention;

FIG. 11 shows magnetic fluxes of a known antenna unit;

FIG. 12 is a sectional view of the magnetic fluxes of the antenna unitshown in FIG. 11;

FIG. 13 is a sectional view of a magnetic field of the antenna unitshown in FIG. 11; and

FIG. 14 shows an automatic ticket gate including a reader/writer deviceaccording to the embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described withreference to the accompanying drawings.

FIG. 1 shows a structure of a wireless information transmitter/receiveraccording to an embodiment of the present invention. FIG. 2 is a diagramof the equivalent circuit of the wireless informationtransmitter/receiver shown in FIG. 1.

The wireless information transmitter/receiver according to an embodimentwill now be described with reference to FIGS. 1 and 2. A wirelessinformation transmitter/receiver 1 includes an IC card 10 and areader/writer device 20, which respectively correspond to a wirelessinformation storage medium and a reader/writer device according to thepresent invention.

The IC card 10 has an antenna coil 100 which constitutes an antennaitself, an IC chip 120, and a tuning capacitor 140 to tune a signalfrequency of the antenna.

The IC chip 120 incorporates a rectifier circuit 121, a stabilized powersupply circuit 122, modulator-demodulator circuits 123 and 124, a memory125, and a CPU or a sequencer 126. Data is written into and read fromthe memory 125 by wireless communication with the reader/writer device20.

The reader/writer device 20 includes an antenna unit 200, whichfunctions as an antenna and corresponds to the antenna unit according tothe present invention, a modulator-demodulator circuit 210, and a CPU220. The reader/writer device 20 transmits data to the IC card 10 byflowing electric currents modulated from 13.56 MHz carrier withtransmitting data to an antenna coil, and receives data from the IC card10 by flowing unmodulated electric currents to the antenna coil. Themodulator-demodulator circuit 210 and the CPU 220 correspond to a signalprocessing circuit according to the present invention.

When the IC card 10 gets close to the antenna coil of the reader/writerdevice 20, terminals of the antenna coil 100 of the IC card 10 producean induced voltage caused by the electromagnetic induction. Accordingly,the IC chip 120 receives a stable power supply voltage from the inducedvoltage and demodulates modulated waves to receive data transmitted fromthe reader/writer device 20.

On the other hand, when the IC card 10 transmits data stored in thememory 125 to the reader/writer device 20, the IC card 10 changes theload Z in accordance with the data. The reader/writer device 20 detectsthe load changes of the antenna coil 100 of the IC card 10 anddemodulates them. Accordingly, the IC card 10 transmits the data to thereader/writer device 20.

Thus, the data is transmitted and received between the IC card 10 andthe reader/writer device 20. Subsequently, a higher level system of thereader/writer device 20, such as a host computer or an informationprocessor in an automatic ticket gate, can utilize the data to, forexample, check passenger tickets or control human entrance.

FIG. 3 is a plan view of a whole antenna unit according to theembodiment of the present invention. FIG. 4 is a sectional view takenalong line IV—IV in FIG. 3.

As shown in FIGS. 3 and 4, an antenna coil of the reader/writer device20 according to the embodiment includes an insulating substrate 201 madeof polyimide (PI) resin or polyethylene naphthalate (PEN) resin. Theinsulating substrate 201 is, for example, 1 mm in thickness. Arectangular loop antenna 202 made of copper or aluminum is formedsubstantially at the center of one of the main surfaces of theinsulating substrate 201. Terminals 202 a at both ends of the loopantenna 202 are connected to a signal processing circuit board, on whichthe modulator-demodulator circuit 210 and the CPU 220 are mounted, viawires.

At the periphery of the four edges of the loop antenna 202, which isdisposed substantially at the center of the insulating substrate 201,conductor segments 203 are formed by the same copper or aluminumconductive pattern as that of the loop antenna 202. The conductorsegments 203 correspond to side lobe suppressing means according to thepresent invention. The conductive pattern of the antenna coil segment,which constitute the loop antenna 202, and the conductor segments 203are, for example, 16 μm in thickness. In particular, the conductivepattern of the conductor segments 203 is preferably uniform inthickness.

In the antenna unit 200 shown in FIG. 3, each of the four rectangularconductor segments 203 is formed at the periphery of the correspondingedge of the rectangular loop antenna 202 and has a predetermined width.The conductor segments 203 are separated from each other for anelectrically insulating purpose. The lengths of the conductor segments203, which are disposed at the periphery of the edges of the loopantenna 202, are preferably greater than or substantially equal to thoseof respective edges of the loop antenna 202. The widths of the conductorsegments 203 are preferably large. This is because a length greater thanthat of the antenna coil segment and the largest possible width easilysuppress an occurrence of the side lobe S. The details are describedbelow.

However, the conductor segments 203 may be formed as follows, inaccordance with the application of the wireless informationtransmitter/receiver 1 (for example, an information processing of ticketgate, an entrance control, or a register information processing), aposition and layout of the antenna unit 200, or the IC card 10approaching direction.

FIGS. 5 to 8 are plan views of whole antenna units 200 according toother embodiments.

An antenna unit 200 shown in FIG. 5 has a rectangular loop antenna 202on one of the main surfaces of the insulating substrate 201. Theconductor segments 203 are formed at the periphery of three out of thefour edges of the loop antenna coil 202. An antenna unit 200 shown inFIG. 6 has a rectangular loop antenna 202 on one of the main surfaces ofthe insulating substrate 201. The conductor segments 203 are formed atthe periphery of two out of the four edges of the loop antenna coil 202.Further, an antenna unit 200 shown in FIG. 7 has a rectangular loopantenna 202 on one of the main surfaces of the insulating substrate 201.The conductor segment 203 is formed at the periphery of one out of thefour edges of the loop antenna coil 202.

In these modifications, peripheral areas of the edges where theconductor segments 203 are not disposed are preferably used for areaswhere the IC card 10 does not approach or the IC card 10 is difficult toapproach depending on a position of the antenna unit 200. The conductorsegments 203 require their own spaces, thus increasing the size of theantenna unit 200. Accordingly, the antenna unit 200 can be compact andcost-effective by mounting the conductor segments 203 in the minimumarea that effectively suppresses a communication error caused by theoccurrence of the side lobe S.

FIG. 14 shows an example in which the reader/writer device is mounted inan automatic ticket gate for railroads. As shown in FIG. 14, anautomatic ticket gate 30 includes the reader/writer device 20, whichreads ticket information stored in the contactless IC card 10, on thetop surface of the body of the automatic ticket gate 30. A rectangularantenna unit 200 is disposed on the entrance side of the top surface ofthe automatic ticket gate 30 and generates a main lobe on the upperspace by the antenna coil to communicate with the contactless IC card10. Passengers often mistakingly hold out the IC card 10 at a positionlittle short of the antenna coil in the passing direction or outside ofthe inside edge, namely, a passenger side of the antenna coil segment.In this case, as shown in FIG. 6, the conductor segments 203 aredisposed on two sides closer to the passenger in the passing directionshown by arrow in FIG. 6, and not on the other two sides. This structureprovides both prevention of a communication error and the compact,low-cost antenna unit 200. The conductor segments 203 may be disposed onthe proximal side and the distal side, and not on right and left sides.Examples shown in FIGS. 5 to 7 are not limited to an automatic ticketgate, and various other changes and modifications can be made therein.

Additionally, a shape of the antenna coil segment of the antenna unit200 is not limited to the rectangular loop shown in FIGS. 3 to 7. Forexample, a circular loop shown in FIG. 8 may be employed. In thisexample, a circular-loop antenna coil segment is formed on one of themain surfaces of the insulating substrate 201. At the periphery of theantenna coil, four conductor segments 203 are disposed at equiangularlycircumferentially spaced locations around the antenna coil segment.However, the conductor segments 203 need not be disposed at fourequiangularly circumferentially spaced locations. The conductor segment203 may be disposed in at least part of the peripheral area of thecircular loop antenna coil.

With reference again to FIGS. 3 and 4, the insulating substrate 201 andthe antenna coil segment can be produced from an insulating substrate ofa predetermined size bonded with a copper or aluminum film. The copperor aluminum film is patterned into a desired antenna coil segment, andthen unnecessary parts are removed by etching. In this case, theconductor segments 203 are formed in the same patterning and etchingsteps. Manufacturing the antenna coil segment and the conductor segments203 in the same patterning and etching steps decreases the totalmanufacturing steps and the cost. In addition, since the antenna coilsegment and the conductor segments 203 are formed by patterning andetching, positioning accuracy is remarkably improved. Furthermore, onlyinitial adjustment of the tuning frequency is necessary, thusconsiderably simplifying the adjustment.

Thus, the antenna unit 200 is achieved. Additionally, filler resinlayers 204 made of epoxy resin and also external packaging resin layersmade of polyethylene terephthalate may be formed on both main surfacesof the antenna unit 200. FIG. 4 shows an example in which only thefiller resin layer 204 is formed.

The principle that suppresses an occurrence of the side lobe S will nowbe described.

An electric field E generated by the conductor segments 203 havinguniform thicknesses is formed perpendicularly on a main surface of theconductor segments 203. Since an electromagnetic field H formed here isperpendicular to the electric field E, no electromagnetic fields Hperpendicular to the conductor segments 203 exist.

FIGS. 9 and 10 are sectional views of the magnetic fluxes and themagnetic fields of the antenna coil according to the embodiment,respectively. In FIGS. 9 and 10, the conductor segments 203 are formedat the periphery of the two opposing edges of the antenna coil segment.As described above, the electromagnetic fields H perpendicular to themain surface of the conductor segments 203 do not occur. A distributionof the magnetic fluxes is shown by dashed lines in FIG. 9. A magneticfield corresponding to the distribution is shown by dashed lines in FIG.10, in which the main lobe M spreads towards the conductor segments 203,that is, W becomes wider than a conventional W, and the side lobes S,which should occur in the areas associated with the conductor segments203, disappear.

Consequently, when the antenna coil 100 of the IC card 10 approaches theconductor segments 203 in parallel, an induced voltage does not occur inthe antenna coil 100, and therefore a communication, such as exchange ofinitial information, between the IC card 10 and the reader/writer device20 is not performed. This eliminates a communication error due to apresence of the side lobes S, as described above. Also, the main lobe Mexpands towards the conductor segments 203.

The above-described embodiments are described merely for purposes ofillustration and are not limited to the present invention. Therefore,various changes and modifications can be made to the elements and theirequivalents disclosed in the embodiments without departing from thespirit and scope of the invention.

For example, although the antenna coil is formed on one surface of theinsulating substrate 201 in the above-described embodiments, the antennacoil may be composed of transmitting and receiving antenna coils, whichare separately mounted on two surfaces of the insulating substrate 201.In this case, the conductor segments 203 may be disposed on either onesurface or both surfaces of the insulating substrate 201.

As described above, according to the present invention, an antenna unitthat prevents a communication error by suppressing side lobes formed byan antenna coil segment of a reader/writer device, and a reader/writerdevice, an information processing system and a communication methodincluding the antenna unit can be provided. Also, a method formanufacturing the antenna unit can be provided.

1. A reader/writer device comprising: an antenna unit including aninsulating substrate, a loop antenna coil on the insulating substrate,and conductor segments formed at the periphery of the antenna coil, theantenna coil and the conductor segments being in substantially the sameplane to generate an electric field which is perpendicular on a mainsurface of the conductor segments to thereby suppress an occurrence ofside lobes in the reader/writer device; wireless communication means fortransmitting data to and receiving data from a wireless informationstorage medium in the form of electromagnetic waves output from theantenna coil; and a processing circuit for processing the data.
 2. Thereader/writer device according to claim 1, wherein the loop antenna coilis rectangular or circular.
 3. The reader/writer device according toclaim 2, wherein the conductor segments are disposed at the periphery ofat least one of the edges of the rectangular ioop antenna coil.
 4. Thereader/writer device according to claim 3, wherein the length of theconductor segments is greater than or substantially equal to the lengthof one of the edges of the rectangular loop antenna coil, and the widthof the conductor segments is greater than the width of the rectangularloop antenna coil.
 5. The reader/writer device according to claim 1,wherein the conductor segments are electrically discontinuous.
 6. Thereader/writer device according to claim 1, wherein the conductorsegments are disposed in the areas adjacent to the proximal end and theinner side of the antenna coil in the moving direction of the wirelessinformation storage medium.
 7. The reader/writer device according toclaim 1, wherein the conductor segments are disposed in the areasadjacent to the proximal end and the distal end of the antenna coil inthe moving direction of the wireless information storage medium.
 8. Thereader/writer device according to claim 1, wherein the conductorsegments and the antenna coil are formed of a single conductivematerial.
 9. The reader/writer device according to claim 1, wherein theconductor segments and the antenna coil are formed by patterning aconductive layer on a main surface of the insulating substrate with anetching process.
 10. An automatic ticket gate for checking ticketscomprising a reader/writer device, said reader/writer device comprising:an antenna unit including an insulating substrate, a loop antenna coilon the insulating substrate, and conductor segments formed at theperiphery of the antenna coil, the antenna coil and the conductorsegments being in substantially the same plane to generate an electricfield which is perpendicular on a main surface of the conductor segmentsto thereby suppress an occurrence of side lobes in the reader/writerdevice; wireless communication means for transmitting data to andreceiving data from a wireless information storage medium in the form ofelectromagnetic waves output from the antenna coil; and a processingcircuit for processing the data.